American Association for the Surgery of Trauma/American College of Surgeons-Committee on Trauma Clinical Protocol for inpatient venous thromboembolism prophylaxis after trauma.

ABSTRACT: Trauma patients are at increased risk of venous thromboembolism (VTE), which includes both deep vein thrombosis and pulmonary embolism. Pharmacologic VTE prophylaxis is a critical component of optimal trauma care that significantly decreases VTE risk. Optimal VTE prophylaxis protocols must manage the risk of VTE with the competing risk of hemorrhage in patients following significant trauma. Currently, there is variability in VTE prophylaxis protocols across trauma centers. In an attempt to optimize VTE prophylaxis for the injured patient, stakeholders from the American Association for the Surgery of Trauma and the American College of Surgeons-Committee on Trauma collaborated to develop a group of consensus recommendations as a resource for trauma centers. The primary goal of these recommendations is to help standardize VTE prophylaxis strategies for adult trauma patients (age ≥15 years) across all trauma centers. This clinical protocol has been developed to (1) provide standardized medication dosing for VTE prophylaxis in the injured patient; and (2) promote evidence-based, prompt VTE prophylaxis in common, high-risk traumatic injuries. LEVEL OF EVIDENCE: Therapeutic/Care Management; Level V.

Effect of Airway Pressure Release Ventilation on Dynamic Alveolar Heterogeneity.

IMPORTANCE: Ventilator-induced lung injury may arise from heterogeneous lung microanatomy, whereby some alveoli remain collapsed throughout the breath cycle while their more compliant or surfactant-replete neighbors become overdistended, and this is called dynamic alveolar heterogeneity. OBJECTIVE: To determine how dynamic alveolar heterogeneity is influenced by 2 modes of mechanical ventilation: low tidal-volume ventilation (LTVV) and airway pressure release ventilation (APRV), using in vivo microscopy to directly measure alveolar size distributions. DESIGN, SETTING, AND PARTICIPANTS: In a randomized, nonblinded laboratory animal study conducted between January 2013 and December 2014, 14 rats (450-500 g in size) were randomized to a control group with uninjured lungs (n = 4) and 2 experimental groups with surfactant deactivation induced by polysorbate lavage: the LTVV group (n = 5) and the APRV group (n = 5). For all groups, a thoracotomy and in vivo microscopy were performed. Following lung injury induced by polysorbate lavage, the LTVV group was ventilated with a tidal volume of 6 mL/kg and progressively higher positive end-expiratory pressure (PEEP) (5, 10, 16, 20, and 24 cm H2O). Following lung injury induced by polysorbate lavage, the APRV group was ventilated with a progressively shorter time at low pressure, which increased the ratio of the end-expiratory flow rate (EEFR) to the peak expiratory flow rate (PEFR; from 10% to 25% to 50% to 75%). MAIN OUTCOMES AND MEASURES: Alveolar areas were quantified (using PEEP and EEFR to PEFR ratio) to determine dynamic heterogeneity. RESULTS: Following lung injury induced by polysorbate lavage, a higher PEEP (20-24 cm H2O) with LTVV resulted in alveolar occupancy (reported as percentage of total frame area) at inspiration (39.9%-42.2%) and expiration (35.9%-38.7%) similar to that in the control group (inspiration 53.3%; expiration 50.3%; P > .01). Likewise, APRV with an increased EEFR to PEFR ratio (50%-75%) resulted in alveolar occupancy at inspiration (46.7%-47.9%) and expiration (40.2%-46.6%) similar to that in the control group (P > .01). At inspiration, the distribution of the alveolar area of the control group was similar to that of the APRV group (P > .01) (but not to that of the LTVV group [P < .01]). A lower PEEP (5-10 cm H2O) and a decreased EEFR to PEFR ratio (≤50%) demonstrated dynamic heterogeneity between inspiration and expiration (P < .01 for both) with a greater percentage of large alveoli at expiration. Dynamic alveolar homogeneity between inspiration and expiration occurred with higher PEEP (16-24 cm H2O) (P > .01) and an increased EEFR to PEFR ratio (75%) (P > .01). CONCLUSIONS AND RELEVANCE: Increasing PEEP during LTVV increased alveolar recruitment and dynamic homogeneity but had a significantly different alveolar size distribution compared with the control group. By comparison, reducing the time at low pressure (EEFR to PEFR ratio of 75%) in the APRV group provided dynamic homogeneity and a closer approximation of the dynamics observed in the control group.

Mechanical breath profile of airway pressure release ventilation: the effect on alveolar recruitment and microstrain in acute lung injury.

IMPORTANCE: Improper mechanical ventilation settings can exacerbate acute lung injury by causing a secondary ventilator-induced lung injury. It is therefore important to establish the mechanism by which the ventilator induces lung injury to develop protective ventilation strategies. It has been postulated that the mechanism of ventilator-induced lung injury is the result of heterogeneous, elevated strain on the pulmonary parenchyma. Acute lung injury has been associated with increases in whole-lung macrostrain, which is correlated with increased pathology. However, the effect of mechanical ventilation on alveolar microstrain remains unknown. OBJECTIVE: To examine whether the mechanical breath profile of airway pressure release ventilation (APRV), consisting of a prolonged pressure-time profile and brief expiratory release phase, reduces microstrain. DESIGN, SETTING, AND PARTICIPANTS: In a randomized, nonblinded laboratory animal study, rats were randomized into a controlled mandatory ventilation group (n = 3) and an APRV group (n = 3). Lung injury was induced by polysorbate lavage. A thoracotomy was performed and an in vivo microscope was placed on the lungs to measure alveolar mechanics. MAIN OUTCOMES AND MEASURES: In the controlled mandatory ventilation group, multiple levels of positive end-expiratory pressure (PEEP; 5, 10, 16, 20, and 24 cm H2O) were tested. In the APRV group, decreasing durations of expiratory release (time at low pressure [T(low)]) were tested. The T(low) was set to achieve ratios of termination of peak expiratory flow rate (T-PEFR) to peak expiratory flow rate (PEFR) of 10%, 25%, 50%, and 75% (the smaller this ratio is [ie, 10%], the more time the lung is exposed to low pressure during the release phase, which decreases end-expiratory lung volume and potentiates derecruitment). Alveolar perimeters were measured at peak inspiration and end expiration using digital image analysis, and strain was calculated by normalizing the change in alveolar perimeter length to the original length. Macrostrain was measured by volume displacement. RESULTS: Higher PEEP (16-24 cm H2O) and a brief T(low) (APRV T-PEFR to PEFR ratio of 75%) reduced microstrain. Microstrain was minimized with an APRV T-PEFR to PEFR ratio of 75% (mean [SEM], 0.05 [0.03]) and PEEP of 16 cm H2O (mean [SEM], 0.09 [0.08]), but an APRV T-PEFR to PEFR ratio of 75% also promoted alveolar recruitment compared with PEEP of 16 cm H2O (mean [SEM] total inspiratory area, 52.0% [2.9%] vs 29.4% [4.3%], respectively; P < .05). Whole-lung strain was correlated with alveolar microstrain in tested settings (P < .05) except PEEP of 16 cm H2O (P > .05). CONCLUSIONS AND RELEVANCE: Increased positive-end expiratory pressure and reduced time at low pressure (decreased T(low)) reduced alveolar microstrain. Reduced microstrain and improved alveolar recruitment using an APRV T-PEFR to PEFR ratio of 75% may be the mechanism of lung protection seen in previous clinical and animal studies.

Airway pressure release ventilation prevents ventilator-induced lung injury in normal lungs.

IMPORTANCE: Up to 25% of patients with normal lungs develop acute lung injury (ALI) secondary to mechanical ventilation, with 60% to 80% progressing to acute respiratory distress syndrome (ARDS). Once established, ARDS is treated with mechanical ventilation that can paradoxically elevate mortality. A ventilation strategy that reduces the incidence of ARDS could change the clinical paradigm from treatment to prevention. OBJECTIVES: To demonstrate that (1) mechanical ventilation with tidal volume (VT) and positive end-expiratory pressure (PEEP) settings used routinely on surgery patients causes ALI/ARDS in normal rats and (2) preemptive application of airway pressure release ventilation (APRV) blocks drivers of lung injury (ie, surfactant deactivation and alveolar edema) and prevents ARDS. DESIGN, SETTING, AND SUBJECTS: Rats were anesthetized and tracheostomy was performed at State University of New York Upstate Medical University. Arterial and venous lines, a peritoneal catheter, and a rectal temperature probe were inserted. Animals were randomized into 3 groups and followed up for 6 hours: spontaneous breathing ventilation (SBV, n = 5), continuous mandatory ventilation (CMV, n = 6), and APRV (n = 5). Rats in the CMV group were ventilated with Vt of 10 cc/kg and PEEP of 0.5 cm H2O. Airway pressure release ventilation was set with a P(High) of 15 to 20 cm H2O; P(Low) was set at 0 cm H2O. Time at P(High) (T(High)) was 1.3 to 1.5 seconds and a T(Low) was set to terminate at 75% of the peak expiratory flow rate (0.11-0.14 seconds), creating a minimum 90% cycle time spent at P(High). Bronchoalveolar lavage fluid and lungs were harvested for histopathologic analysis at necropsy. RESULTS: Acute lung injury/ARDS developed in the CMV group (mean [SE] PaO2/FiO2 ratio, 242.96 [24.82]) and was prevented with preemptive APRV (mean [SE] PaO2/FIO2 ratio, 478.00 [41.38]; P < .05). Airway pressure release ventilation also significantly reduced histopathologic changes and bronchoalveolar lavage fluid total protein (endothelial permeability) and preserved surfactant proteins A and B concentrations as compared with the CMV group. CONCLUSIONS AND RELEVANCE: Continuous mandatory ventilation in normal rats for 6 hours with Vt and PEEP settings similar to those of surgery patients caused ALI. Preemptive application of APRV blocked early drivers of lung injury, preventing ARDS. Our data suggest that APRV applied early could reduce the incidence of ARDS in patients at risk.

Early stabilizing alveolar ventilation prevents acute respiratory distress syndrome: a novel timing-based ventilatory intervention to avert lung injury.

BACKGROUND: Established acute respiratory distress syndrome (ARDS) is often refractory to treatment. Clinical trials have demonstrated modest treatment effects, and mortality remains high. Ventilator strategies must be developed to prevent ARDS. HYPOTHESIS: Early ventilatory intervention will block progression to ARDS if the ventilator mode (1) maintains alveolar stability and (2) reduces pulmonary edema formation. METHODS: Yorkshire pigs (38-45 kg) were anesthetized and subjected to a "two-hit" ischemia-reperfusion and peritoneal sepsis. After injury, animals were randomized into two groups: early preventative ventilation (airway pressure release ventilation [APRV]) versus nonpreventative ventilation (NPV) and followed for 48 hours. All animals received anesthesia, antibiotics, and fluid or vasopressor therapy as per the Surviving Sepsis Campaign. Titrated for optimal alveolar stability were the following ventilation parameters: (1) NPV group--tidal volume, 10 mL/kg + positive end-expiratory pressure - 5 cm/H2O volume-cycled mode; (2) APRV group--tidal volume, 10 to 15 mL/kg; high pressure, low pressure, time duration of inspiration (Thigh), and time duration of release phase (Tlow). Physiological data and plasma were collected throughout the 48-hour study period, followed by BAL and necropsy. RESULTS: APRV prevented the development of ARDS (p < 0.001 vs. NPV) by PaO2/FIO2 ratio. Quantitative histological scoring showed that APRV prevented lung tissue injury (p < 0.001 vs. NPV). Bronchoalveolar lavage fluid showed that APRV lowered total protein and interleukin 6 while preserving surfactant proteins A and B (p < 0.05 vs. NPV). APRV significantly lowered lung water (p < 0.001 vs. NPV). Plasma interleukin 6 concentrations were similar between groups. CONCLUSION: Early preventative mechanical ventilation with APRV blocked ARDS development, preserved surfactant proteins, and reduced pulmonary inflammation and edema despite systemic inflammation similar to NPV. These data suggest that early preventative ventilation strategies stabilizing alveoli and reducing pulmonary edema can attenuate ARDS after ischemia-reperfusion and sepsis.

A surgical rat model of human Roux-en-Y gastric bypass.

Obesity affects 30% of the United States population and its detrimental effects are obesity-related metabolic diseases. For patients refractory to conventional weight loss therapy, gastric bypass surgery is one of the proven methods for inducing a sustained weight loss and reversing the metabolic sequelae of obesity. To understand the mechanisms of weight loss and the amelioration of related metabolic comorbid conditions, a reproducible animal model is needed. We report our developmental experience with rat models of sequential Roux-en-Y gastric bypass after reproducing the diet-induced obesity that characterizes the hallmarks of human obesity. Four experiments were performed to induce weight reduction through successive modifications: In Experiment 1 a 20% stapled gastric pouch with a 16 cm biliary-pancreatic limb and a 10 cm alimentary limb accomplished sufficient weight loss within 10 days to ameliorate metabolic changes associated with obesity, but the occurrence of gastrogastric fistulas prevented sustained weight loss; in Experiment 2 the model was improved by dividing the stomach to avoid gastrogastric fistula, but again sustained weight loss was not achieved; in Experiment 3 the biliary-pancreatic limb was lengthened from 16 to 30 cm, reducing the common channel to approximately 18 cm. Sustained weight loss was achieved for 28 days. In Experiment 4 the model in Experiment 3 was modified by dividing the stomach between two rows of staples. Sustained weight loss was observed for 67 days. We developed a reproducible rat model of Roux-en-Y gastric bypass. The existence of this model opens a new field of research in which to study the metabolic sequelae of obesity and the mechanisms of weight loss.

Radiation dose to the operator during vertebroplasty: prospective comparison of the use of 1-cc syringes versus an injection device.

BACKGROUND AND PURPOSE: Percutaneous vertebroplasty procedures require relatively long durations of fluoroscopic guidance, which might lead to substantial radiation dose to operators. Specialized injection devices have been proposed to limit operator exposure. Our purpose was to compare the radiation dose to the operator's hands during vertebroplasty when using 1-cc syringes versus that when using an injection device. METHODS: Radiation dosimeters were worn on the left wrist during 39 vertebroplasty injection procedures in 25 patients. Cases were alternated between the use of 1-cc syringes (19 procedures) and the use of an injection device (20 procedures). For each procedure, one dosimeter was worn throughout the procedure, both during needle placement and injection, and a second dosimeter was worn during the injection phase only. Mean doses for the whole case and mean doses for the injection procedure alone were compared between groups. RESULTS: Mean whole case dose was 128 +/- 161 mrem (range, 0-660 mrem) for the 1-cc syringe group versus 98 +/- 90 mrem (range, 0-340 mrem) for the injection device group (P =.23). Mean dose during injection was 100 +/- 145 mrem (range, 0-660 mrem) for the 1-cc syringe group versus 55 +/- 43 mrem (range, 0-130 mrem) for the injection device group (P =.09). Three of 19 1-cc syringe cases yielded zero dose, compared with four of 20 injection device cases. Duration of injection was markedly different between groups, with mean injection times of 4.2 and 7.5 min for 1-cc syringe and injection device cases, respectively (P <.00002). Mean injection dose per minute of lateral fluoroscopy was 23.6 and 7.3 mrem for the 1-cc syringe and injection device groups, respectively (P =.002). CONCLUSION: The use of an injection device significantly decreased the radiation dose to the operator's extremity per unit time of injection. However, total dose per injection was equivalent between groups because of significantly longer injection duration for the injection device cohort.

Comparison of conscious sedation and general anesthesia for motor mapping and resection of tumors located near motor cortex.

OBJECT: The surgical treatment of tumors located near eloquent cortex carries a high risk of inducing worsening neurological deficits. Intraoperative electrocorticography techniques have been developed to help identify these areas at the time of surgery in an effort to minimize such risks. The optimal anesthetic technique for conducting these procedures, however, has never been determined. METHODS: The authors conducted a retrospective study to compare patients who underwent intraoperative motor mapping between September 2000 and May 2002. Demographic and neurophysiological monitoring data were collected from the hospital records. Patients were divided into two groups based on the anesthetic technique used for surgery: in Group 1 general anesthesia was used, and in Group 2 conscious sedation. Group 1 comprised 24 patients (mean age 47 years) with 16 right- and eight left-sided lesions. Group 2 consisted of 21 patients (mean age 46 years) with 18 right- and three left-sided lesions. Pathological diagnoses were similar between the two groups. Motor stimulation was elicited in 12 patients (50%) in Group 1 and in 21 patients (100%) in Group 2 (p < 0.001). In addition, the mean stimulation amplitude required was significantly higher (13 mA) in patients in whom conscious sedation was used as opposed to general anesthesia (5 mA, p < 0.0001). Electrographic evidence of seizures was seen in 29% of Group 1 compared with 10% of Group 2 patients (p > 0.05). CONCLUSIONS: The use of conscious sedation as an anesthetic technique for motor mapping not only improves the chances of achieving successful stimulation and identification of motor cortex in relationship to the lesion, but it also allows for repetitive monitoring of the patient's motor function during resection of the lesion.

The therapeutic benefit of repeat percutaneous vertebroplasty at previously treated vertebral levels.

BACKGROUND AND PURPOSE: Recurrent pain after vertebroplasty is relatively common, usually representing a new fracture at a different vertebral level. In a small cohort described herein, clinical and imaging findings indicated that recurrent pain arose from abnormality of the previously treated level. Our purpose was to demonstrate that repeat percutaneous vertebroplasty performed within the same fractured vertebra can offer therapeutic benefit for patients with recurrent pain after initial treatment. METHODS: We conducted a retrospective review of consecutive vertebroplasty procedures performed at our institution to define a patient population that underwent repeat vertebroplasty for recurrent pain at previously treated vertebral levels. We identified six such patients over an 8-year period, and clinical outcomes were assessed through quantitative measurements of pre- and postoperative levels of pain and mobility. RESULTS: Initial vertebroplasty resulted in substantial improvement in pain in all six patients. Patients developed recurrent pain between 8 days and 167 days after initial vertebroplasty. After repeat vertebroplasty, five of the six patients reported a reduction of at least 3 points in their rating of pain, with a mean reduction of 6.5 points and a mean postoperative pain level of 3.5 points (11-point scale). Four of six patients reported impaired mobility before repeat vertebroplasty, and all four demonstrated a postoperative improvement in mobility. Mean increase in mobility was 1.50 points, and the mean postoperative mobility impairment was 0.25 points (5-point scale). CONCLUSION: The clinical outcomes of the patients within this case series suggest that repeat percutaneous vertebroplasty performed at previously treated vertebral levels for recurrent pain offer therapeutic benefit.

Vertebroplasty in the mid- and upper thoracic spine.

BACKGROUND AND PURPOSE: Vertebroplasty performed in the mid- and upper thoracic spine presents technical challenges that differ from those in the lower thoracic and lumbar region. We herein report results of percutaneous vertebroplasty for treatment of painful, osteoporotic compression fractures in the mid- and upper thoracic spine. METHODS: Retrospective chart review identified vertebroplasty treatments performed for painful osteoporotic compression fractures at T4-T8. The following were catalogued: percentage of vertebral body compression, needle size, surgical approach, clinical outcome, volume of cement injected, and complications. RESULTS: Sixty-three vertebral bodies were treated in 41 patients. Mean percentage of compression was 44%. Bipediculate injections were used in 12 (19%) of 63 treatment levels, and unipediculate injections were used in 51 (81%) of treatments (75 injections performed). Eleven-gauge needles were used for 55 (73%) of the 75 injections, and 13-gauge needles were used for 20 (27%). Clinical follow-up was available for 76% of the patients. Mean pre- and postoperative pain intensity was 9.7 +/- 1.0 and 1.7 +/- 1.9, respectively (P <.0001). Mean pre- and postoperative medication scores were 3.4 +/- 0.7 and 1.7 +/- 1.7, respectively (P =.075). Fracture involving the pedicle used for needle access was noted in one (1.3%) of 75 injections; this pedicle had been traversed using a 13-gauge needle. Staphylococcus epidermidis infection occurred in one case. No cases of pneumothorax were noted. CONCLUSION: Transpedicular vertebroplasty is readily and safely performed using 11-gauge needles in the mid- and upper thoracic regions, yielding excellent pain relief and low complication rates.